Andrew McKinley, 56, carries books to review with business partner Christopher Rolls, 40 (center), to decide which to purchase for their bookstore.

Photo: Leah Millis, The Chronicle

Andrew McKinley, 56, carries books to review with business partner...

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People collect books from a donated selection during the $1 Book Sale January 11, 2014 at the Friends of the San Francisco Public Library Book Donation Center in San Francisco, Calif. The book sale happens every second Saturday on a monthly basis, with the proceeds benefitting the San Francisco Public Library. "You never know what you will find," said Andrew McKinley, 56, a book store owner, while sifting through stacks of books, "you might find a book that will change your thinking, or it might change your life."

Photo: Leah Millis, The Chronicle

People collect books from a donated selection during the $1 Book...

Image 3 of 4

Molly McMahon, 26, searches through donated books during the $1 Book Sale January 11, 2014 at the Friends of the San Francisco Public Library Book Donation Center in San Francisco, Calif. The book sale happens every second Saturday on a monthly basis, with the proceeds benefitting the San Francisco Public Library. "You never know what you will find," said Andrew McKinley, 56, a book store owner, while sifting through stacks of books, "you might find a book that will change your thinking, or it might change your life."

Photo: Leah Millis, The Chronicle

Molly McMahon, 26, searches through donated books during the $1...

Image 4 of 4

Casey Tran, 23, clutches a stack of found books for purchase during the $1 Book Sale January 11, 2014 at the Friends of the San Francisco Public Library Book Donation Center in San Francisco, Calif. The book sale happens every second Saturday on a monthly basis, with the proceeds benefitting the San Francisco Public Library. "You never know what you will find," said Andrew McKinley, 56, a book store owner, while sifting through stacks of books, "you might find a book that will change your thinking, or it might change your life."

Photo: Leah Millis, The Chronicle

Casey Tran, 23, clutches a stack of found books for purchase during...

Someone, somewhere, must need "The Theory of Poker." Scott Bravmann was counting on it, and he wasn't even the author.

So Bravmann dropped $1 for the 1983 paperback at the Friends of the San Francisco Public Library's dollar-a-book sale Saturday in the Mission District, hoping to flip it for a minimum 100 percent profit. Such bets helped him gross more than $100,000 last year selling books on the Internet, he said.

"I make a living," he shrugged, his arms filled with the decaying seeds of his wealth.

Anyone who thinks physical books are dead might want to show up at 438 Treat Ave. on the second Saturday of each month, where the library typically sells $1,000 of used books - part of the $1.3 million it takes in annually from selling real books to consenting adults and children.

Yet appearances can be deceiving. Among the dozens of people who browsed, bought and donated books at the library warehouse, finding people who were there simply to buy a cheap book and read it wasn't easy.

One woman walked back and forth waving a small device over each book like a dowser with a divining rod, scanning them to determine their resale value.

The prospect of buying low and selling high also drew 20-year-old Tenae Stewart all the way from Lake County, some 90 miles away. She made a few hundred dollars last year selling "vintage" books on the Web.

"You find really great things at sales like this," she said, opening her bag to reveal a Nancy Drew mystery, a 1946 hardcover of "Animal Farm," and a "Hans Brinker" with the inscription, "To Jack from Mrs. Oppermann, Dec. 1938."

"People are buying books," she said, though admitted she'd just bought an e-reader.

Stewart wasn't the only customer whose hair still had color.

Casey Tran, 23, clutched a pair of paperbacks - Alan Watts' classic "The Book: On the Taboo Against Knowing Who You Are," and the less classic "Pictorial Key to the Tarot," by A.E. Waite. Tran, who recently graduated with a marketing degree from San Francisco State, said she was just picking up something to read until she could afford to buy an e-reader.

"I like Kindles because you can put a lot of books inside," she said.

It's an approach that rankles book lovers like Bill, 46, who declined to give his last name. Bill was stuffing a backpack with books on Florentine art, Swiss aerial photography, Mexican pottery and other subjects.

"I'm just shocked at how willingly people will subvert their life to a rectangle they carry with them," he said. "In an age of e-books, these won't be around soon - kind of like records."

Luis Zuniga, 48, was also there to buy books for reading, even though he's a library employee.

"To keep a book and be edified by it again and again," he said, his voice trailing off. "You can also smell books, especially the leather-bound ones, which prompt memories.

"For me, books take me to a time when everything was new and when the road not traveled was still there for me to decide upon."